Due to ageing processes when storing colour films, colour distortions arise because the colour particles within the emulsion slowly follow the force of gravity (grain migration). This often affects red colour particles in the case of reversal films, while a distortion of the colours yellow and cyan arises in the case of colour negative films. These colour distortions become apparent for example such that an intrinsically single-coloured horizontal line which contains the relevant colour changes colour over its length.
The distortion of the respective colour component caused by the grain migration is essentially constant over the entire film—assuming the film was not composed of segments stored for different lengths of time or, if appropriate, comprising different materials.